The present invention relates to a recording sheet conveyor apparatus in a recording apparatus such as a laser beam recorder or the like, and more specifically relates to a recording sheet conveyor apparatus having a recording sheet housing means to house the recording sheets that are the recording medium, an information recording means to draw the recording sheets from the recording sheet housing means and to record image information upon the sheets when they are moving, and a sheet receiving means to receive discharged sheets upon which image information has been recorded, and which is applicable to image recording apparatus.
FIG. 1A and FIG. 1B indicate conventional recording sheet conveyor apparatus. The conventional apparatus shown in FIG. 1A comprises a conveyor path 15 between a cassette 2 housing a recording sheet 1 and a sheet receiving device 16. Along the conveyor path 15 is provided a main roller 3 to send the recording sheets 1 at a predetermined speed to a recording position in a recording unit 11. Three feed rollers 4, 5 and 6 are provided along the conveyor path 15 between the cassette 2 and the main roller 3 to feed the recording sheets 1 to the main roller 3. In addition, along the conveyor path 15 and between the main roller 3 and the sheet receiving device 16 is provided a discharge roller 12 to feed recording sheets 1 upon which recording has been performed, to the sheet receiving device 16. Each of the feed rollers 4, 5 and 6 have a drive roller 7 which is linked to a motor, and a nip roller 8 which rotates in accordance with the rotation of a drive roller 7 and together with the drive roller 7 holds the recording sheet 1. The main roller 3 comprises a main drive roller 9 and a pair of nip rollers 10a, 10b. The main drive roller 9 is linked to the main motor, and the nip rollers 10a, 10b are positioned before and after the main drive roller 9. The recording sheet 1 is held between the main roller 9 and the nip rollers 10a, 10b. The nip rollers 10a, 10b rotate along with the rotation of the main drive roller 9. In the same way as the feed roller, the discharge roller 12 also has a nip roller 14 and a drive roller 13 linked to a motor.
In an information recording apparatus having this configuration, in order to obtain a high image quality, it is necessary to convey the recording sheet 1 at a constant speed when recording by the main roller is being performed, so that unwanted external forces are not applied to the recording sheet 1.
One example of an image recording apparatus in which the recording sheets 1 are conveyed at a constant-speed so that unwanted external forces do not apply is disclosed in Japanese Patent Laid-Open Publication No. 100867-1988.
According to this invention, a recording sheet positioned immediately before the main roller 3 is made to assume a loop shape and the main roller 3 feeds the recording sheet 1 in a state where external forces are not applied. Also, the discharge roller 12 which is the roller closest to the main roller 3, is driven by the same drive as the main roller 3 when recording is being performed.
In such a conventional recording sheet conveyor apparatus, the main roller 3, the feed rollers 4, 5 and 6, and the discharge roller 12 are all driven when recording is performed. Because of this, the vibration that is created by the drive sources for each of the rollers is transmitted to the recording sheet 1.
In addition, variations in the speed of rotation of the discharge roller 12 cause fluctuations in the load acting upon the recording sheet 1 and these load variations also cause the recording sheet 1 to vibrate. This vibration of the recording sheet 1 during recording causes the quality of the recorded image to drop.
The conventional recording sheet conveyor apparatus indicated in FIG. 1B, simply introduces a recording sheet 1 drawn out from the cassette 2, into the conveyor path 15. The first feed roller 4 has a mechanism to bring a nip roller 8 into contact with a drive roller 7 and to separate the nip roller 8 from the drive roller 7. The recording sheet 1 is inserted between the nip roller 8 and the drive roller 7 in the status when the nip roller 8 is separated from the drive roller 7. Then, the nip roller 8 is pressed against the drive roller 7 and the recording sheet 1 is held between the drive roller 7 and the nip roller 8. When the recording sheet 1 is in this status and the feed rollers 4, 5 and 6 are driven, the recording sheet 1 is sequentially fed toward the main roller 3.
In such a conventional recording sheet conveyor apparatus, any misfeed of the recording sheet 1 in the conveyor path 15 is difficult to rectify since each of the feed rollers 5 and 6 and the like all have the same drive source.
In addition, in a conventional recording sheet conveyor apparatus, the conveyor path 15 is generally provided with a guide plate to guide the recording sheet 1. In the case where a guide plate is provided, a moving recording sheet 1 comes into contact with the inner wall surfaces of the guide plate and the surface of the recording sheet 1 is marked or scratched and static electricity is generated. This static electricity also becomes a cause of recording sheet 1 misfeeds.